Array of components

ABSTRACT

A support element  22  is fitted between adjacent vanes  8, 14  in a gas turbine engine, in order to suppress vibrations in the vanes  8, 14 . The support element  22  comprises a body portion  24  and pad portions  38, 40  which contact the vanes  8, 14  over a wide area to restrain displacement of the vanes  8, 14  while minimising overstressing.

This invention relates to an array of similar elongate components, andis particularly, although not exclusively, concerned with an array inwhich the components are vanes of a gas turbine engine.

A conventional gas turbine engine comprises an annular passage which isspanned by vanes which serve an aerodynamic function in that they directworking fluid of the engine to an appropriate angle of incidence for adownstream component, such as a bladed rotor. The vanes may also serve astructural function, by providing support for other components of theengine.

The vanes may have inner and/or outer shrouds at their radial ends, andthese shrouds may be interconnected in groups to provide packs of two ormore vanes. Such packs have a significantly increased stiffness comparedto the individual vanes.

Each vane has various vibration modes. A vibrating vane may excitevibration also in adjacent vanes. Such vibrations may reduce the life ofthe vanes themselves and other components of the engine, and may alsorestrict the operating envelope of the engine. Damping of the vibrationsby conventional means may be difficult, particularly for low strainvibration modes, such as torsional modes.

According to the present invention there is provided an array of vanesfor a gas turbine engine, the array being an annular array disposedabout a central axis, and the vanes being assembled in packs, whereineach pack comprises two rows of vanes, the vanes of each pack beingsupported at at least one end by a common support so as to be spacedapart from one another and which, in use, are subjected to excitationinputs which induce vibration in the vanes, a support element beingdisposed between two adjacent vanes in each row, the support elementcomprising respective body portions disposed between the adjacent vanesin each row and a pad portion which extends laterally from each bodyportion, the pad portion having a contact surface which contacts asurface of one of the adjacent components, characterised in that abridge region is provided between the body portion regions.

The body portion may be provided with a said pad portion at each of twoopposite sides of the body portion, the contact surface of each of thepad portions contacting a surface of a respective one of the adjacentvanes.

The body portion may comprise a central web, and the or each pad portionmay be in the form of a flange which projects out of the plane of theweb at an edge of the web. The web may be curved about an axis which isparallel to the gap direction.

The support element is preferably secured to at least one of theadjacent vanes. In one embodiment, securing of the support element maybe achieved by bonding the pad portion, or at least one of the padportions, to the respective vane at the contact surface. Alternativelyor additionally, the support element may be secured by a mechanicalfixing, such as a screw or bolt extending through the pad portion intothe respective vane. Means may be provided for locating the supportelement with respect to the vanes. For example, the support element maybe provided with a projection which is received in an aperture in one ofthe vanes.

The array may comprise an annular array of the vanes disposed about acentral axis, with the vanes extending in a substantially radialdirection from the axis. The vanes of the array may be assembled inpacks, with the vanes of each pack being interconnected by a connectingelement at at least one radial end of the vanes. The packs aresubsequently assembled together to form the complete array. The supportelement may be disposed between adjacent vanes of the same pack, or itmay be disposed between adjacent vanes of adjacent packs. In oneparticular embodiment, a plurality of the support elements aredistributed around the array, with support elements being disposedbetween some, but not all, adjacent pairs of vanes in the array.

For some modes of vibration, it is desirable for the support element tobe situated away from the radial ends of the vanes, for example at aposition substantially midway along the lengths of the vanes. The bodyportion may be provided with an aerodynamic shape conforming to the flowof working fluid between the vanes in operation. The or each pad portionmay also have an aerodynamic flow surface disposed opposite the contactsurface.

If the vanes are assembled as vane packs, each vane pack may comprisetwo or more rows of vanes at different axial positions from each other.In such an array, the body portion of the support element may compriserespective body portion regions disposed between adjacent vanes ofadjacent rows, and a bridge region interconnecting the body portionregions. Each body portion region preferably has at least one of thesaid pad regions. In order to fit between adjacent vanes of differentrows, the body portion regions may be offset from each other in atangential direction.

For a better understanding of the present invention, and to show moreclearly how it may be carried into effect, reference will now be made,by way of example, to the accompanying drawings, in which:

FIG. 1 is a diagrammatic partial axial cross sectional view of a gasturbine engine;

FIG. 2 is a view in the direction of the arrow A in FIG. 1;

FIG. 3 shows a vane pack including a support element;

FIG. 4 shows a vane pack having an alternative embodiment of supportelements;

FIGS. 5 to 8 show various views of the support element of FIG. 3.

FIG. 1 shows, by way of example, part of a compressor section of a gasturbine engine. The compressor section comprises a bladed rotor 2 whichis rotatable about an axis disposed below FIG. 1. The rotor 2 isrotatable within a casing 4, which supports circumferential arrays ofstator vanes 6 and 8. In operation, gas flow through the compressorsection takes place in the direction of the arrow X. The downstreamarray of stator vanes 8 is shown partially in FIG. 2. The array is madeup of a plurality of vane packs 10. The vanes 8 in each pack 10 areconnected together by straps 12 (see FIG. 3). In the embodiment shown inFIG. 2, each vane pack comprises three vanes 8.

FIG. 3 shows a vane pack in more detail. In this instance, the vane packcomprises two circumferentially disposed vane elements, each vaneelement comprising two axially spaced vanes 8, 14 extending betweenshroud portions 16, 18. Thus, an assembled array made up of vane packs10 as shown in FIG. 3 would comprise two rows of vanes 8, 14 disposedwith one axially downstream of the other.

The strap 12 extends across the shroud portions 16 to secure the vaneelements together to form the pack 10. A similar strap 20 is provided atthe radially inner end of the vane pack, interconnecting the innershroud portions 18.

The flow direction X is indicated in FIG. 3, from which it will beappreciated that the leading edges of the vanes 8, 14 face into thepage.

A support element 22 is provided in the vane pack 10. The supportelement 22 extends across both rows of vanes 8 and 14, and extendsbetween adjacent blades 8, 14 of each row. The support element 22 ispositioned away from the ends of the vanes 8, 14, and is generallymidway between the ends. As shown in FIG. 3, the support element 22 issituated slightly radially outwardly beyond the precise midpoint betweenthe ends of the vanes.

The support element 22 is shown in more detail in FIGS. 5 to 8. Itcomprises a body portion 24, generally in the form of a central webwhich extends the full length of the support element in the axialdirection (ie the direction of gas flow X in FIG. 3). The body portioncomprises first and second body portion regions 26, 28, for positioningbetween the respective pairs of vanes 14, 8. The body portion regions 26and 28 are interconnected by a bridge region 30 which, in use, extendsbetween the two rows of vanes 8, 14. As can be appreciated from FIG. 8,the body portion 24 is slightly curved about an axis which extendsgenerally parallel to the direction of the gap between adjacent vanes 8,14, as indicated by an arrow G in FIGS. 3 and 4 (referred to forconvenience as the “gap direction”). The body portion 22 is also curved,about an axis extending generally radially of the vane pack, as shownmost clearly in FIGS. 6 and 7, in order to conform to the shape of thepath between the vanes.

Each body portion region 26, 28 is provided at opposite side edges withlaterally extending pad portions 32, 36 respectively, in the form offlanges projecting from the central web of the body portion 24. Each padportion has a vane contact surface 38, 40 which conforms to the shape ofthe surface of the vane 8, 14 against which the respective contactsurfaces 38, 40 lie in the assembled condition, as shown in FIG. 3.

It will be appreciated that the body portion regions 26, 28 are offsetfrom each other, as shown in FIGS. 5 to 7, in the gap direction G,reflecting the relative positions of the vanes 8 and 14 of the vane pack10.

The support element 22 may be made of any suitable material which canwithstand the temperatures to which it will be exposed in use, which issufficiently stiff to resists loads imposed upon it by vibration of thevanes 8, 14. Suitable materials are glass or carbon reinforced plasticsmaterials, or aerospace alloys of aluminium and/or titanium.

It will be appreciated that the support element 22 fits intimatelybetween the adjacent vanes 8, 14 with the contact surfaces 38, 40 of thepad portions 32, 36 in face-to-face contact with the oppositely facingsurfaces of the vanes 8 and 14. The support element may be configured sothat it locks in position between the vanes 8, 14, or it may be secured,for example by bonding at the contact surfaces 38, 40 or by mechanicalfixings. In an alternative embodiment shown FIG. 4, the support element22 has projections 42 and 44 extending respectively from the bodyportion 24 and one of the pad portions 32, 36. These projections 42 and44 extend into appropriately shaped holes in the vanes 8 to lock thesupport element 22 in position. It will be appreciated that, in theembodiment shown in FIG. 4, the support element 22 must be fitted as thevanes 8 of the vane pack 10 are assembled together or as the vane packs10 are assembled into a complete annular array. However, in otherembodiments, it is possible for the support element 22 to be introducedbetween the vanes 8, 14 after the vane pack 10 has been assembled, andpossibly after the entire array of vanes has been installed in anengine. Thus, in some embodiments, the support elements 22 areretrofitable to an engine without major dismantling of the engine.

The configuration of the body portion 24 and the shapes of surfaces 46,48 on the sides of the pad portions 32, 36 opposite the contact faces38, 40 are designed to minimise the obstruction to the flow of workingfluid through the vane packs 10. Thus, the curved configuration of thebody portion 24 is designed to follow the path taken by the workingfluid between the vanes 8, 14 so as to minimise any pressure drop causedby the support element 22 and to avoid any instability in the flow.

The purpose of the support element 22 is to suppress vibration of thevanes 8, 14 in operation of the engine. Such vibrations may be excitedby aerodynamic effects in the engine, and one vibrating vane can excitevibrations in adjacent vanes. For example, antiphase first torsionalmode vibration may be excited between adjacent vanes 8 or 14 butsuitable positioning of the support element 22 can significantlyrestrain, or even eliminate, these vibrations. Because the pad portions32, 36 extend over the full chordal width of the vanes 8, 14,displacements arising from torsional vibration can be adequatelyresisted in a manner which would not be possible by connecting elementsengaging the vanes over only a small part of the chordal width. Thus, itwill be appreciated that the pad portions 32, 36 should preferablyextend over at least 50%, and more preferably at least 75%, of thechordal width of the vanes 8, 14. Furthermore, because the amplitude ofdisplacements generated by first torsional mode vibration will be at amaximum towards the midpoint between the ends of the vanes 8, 14, it isdesirable, if adequate suppression of the vibration is to be achieved,for the support element 22 to be positioned at, or close to, themidpoint. However, if suppression of higher order harmonics is to beachieved, different positioning of the support element 22, or use ofmultiple support elements 22, may be desirable.

In the embodiment shown in FIG. 3, the vane pack includes two rows ofvanes 8, 14. Because the support element 22 extends between the rows, avane row, for example the vanes 14, which are subject to little or novibration can assist in stabilising vanes in a different row, forexample the vanes 8, which would otherwise be subject to vibration.

Because the pad portions 32, 36 have substantial contact surfaces 38,40, any load on the vanes 8, 14 imposed by the support elements 22 isspread over a significant area of the vane surfaces. Consequently, localoverstressing of the vane 8, 14 or of the support element 22 can beavoided.

As shown in FIGS. 3 and 4, the support element 22 is disposed betweenadjacent vanes 8, 14 in the same vane pack 10. However, it is alsopossible for the support element 22 to be disposed between adjacent vanepacks 10, contacting a vane or vanes of one pack 10 on one side, and ofthe other vane pack 10 on the other side.

The support element 22 may be one of several support elementsdistributed around the array of vanes. A support element 22 need not beprovided in each gap between adjacent vanes 8, 14, although in mostcircumstances each vane 8, 14 would be connected by a support element 22to at least one other vane in the same row. The support elements 22 mayall be at the same radial distance along the vanes 8, 14, at least ineach row of vanes. However, since different vane rows experiencedifferent exciting inputs, the radial position of the support elements22 may be different in different rows.

Because the support element 22 can be retrofitted, it is possible toremedy vibrations which occur in the vanes of an engine in operation,after analysing the causes and nature of the vibrations that occur.

Although the present invention has been described with reference tovanes in a gas turbine engine, it will be appreciated that theunderlying principles of the invention may be applicable also in othertypes of vaneed machinery, or in other circumstances where vibrationsmay be excited in the components of an array. For example, supportelements as described above may also be positioned between adjacentcomponents of aerial arrays, acoustic equipment, or panels formed fromthin skinned components.

1. An array of vanes for a gas turbine engine, the array being an annular array disposed about a central axis, and the vanes being assembled in packs, wherein each pack comprises two rows of vanes, the vanes of each pack being supported at at least one end by a common end support so as to be spaced apart from one another and which, in use, are subjected to excitation inputs which induce vibration in the vanes, a support element being disposed between two adjacent vanes in each row, the support element comprising respective body portions disposed between the adjacent vanes in each row and a pad portion which extends laterally from each body portion, the pad portion having a contact surface which contacts a surface of one of the adjacent components, characterised in that a bridge region is provided between the body portion regions.
 2. An array as claimed in claim 1, characterised in that the body portion regions are offset with respect to each other in a direction (G) extending between the adjacent vanes.
 3. An array as claimed in claim 1, characterised in that the pad portion is one of two pad portions disposed at opposite sides of the body portion, the contact surface of each pad portion contacting a respective one of the adjacent vanes.
 4. An array as claimed in claim 1, characterised in that the body portion comprises a central web, the or each pad portion comprising a flange extending from an edge of the web.
 5. An array as claimed in claim 4, characterised in that the central web is curved about an axis extending parallel to the direction (G) extending between the adjacent vanes.
 6. An array as claimed in claim 1, characterised in that the support element is secured to at least one of the adjacent vanes.
 7. An array as claimed in claim 6, characterised in that the support element is secured to the adjacent vane by bonding at the contact surface.
 8. An array as claimed in claim 6, characterised in that the support element is secured to the adjacent vane by means of a projection on the support element which engages an aperture in the vane.
 9. An array as claimed in claim 1, characterised in that the vanes extend substantially radially with respect to the axis.
 10. An array as claimed in claim 1, characterised in that the vanes of each pack are interconnected by a connecting element at at least one radial end.
 11. An array as claimed in claim 10, characterised in that the support element is disposed between adjacent vanes of a common pack.
 12. An array as claimed in claim 1, characterised in that the support element is disposed between adjacent vanes of adjacent packs.
 13. An array as claimed in claim 1, characterised in that the support element is disposed substantially midway between the ends of the vanes.
 14. An array as claimed in claim 1, characterised in that the body portion has an aerodynamic profile conforming to fluid flow in use between the vanes.
 15. An array as claimed in claim 1, characterised in that each pad portion has an aerodynamic flow surface on a side of the pad portion opposite the contact surface.
 16. An array as claimed in claim 1 characterised in that the array has a plurality of support elements, and the support elements are disposed between some only of the vanes of the array.
 17. A support element for use in an array of vanes for a gas turbine engine in accordance with claim
 1. 